JP2007101726A - Exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure device capable of obtaining stable printing quality. <P>SOLUTION: A driving voltage applied on an organic EL light emitting element in order to drive the organic EL light emitting element 20 with a constant current is measured by a voltage measuring part 38 included in a drive circuit 30, then, light emission area information showing a relation between the driving voltage and the light emission area as the light emitting region of the organic EL light emitting element 20 is stored in a ROM 45B, and gradation characteristics information showing the gradation characteristics of the photosensitive material when the light is emitted from the organic EL light emitting element 20 in each light emission area is prestored for every predetermined light emission areas, and in a system control part 45, the light emission area is derived from the driving voltage measured by the voltage measuring part 38 based on the light emission area information stored in the ROM 45B, and the gradation characteristics information corresponding to the derived light emission area is selected out of the gradation characteristics information for every light emission area stored in the gradation characteristics information storage part 46, and then, in the gradation conversion part 42, the gradation conversion related to image data is performed by using the selected gradation characteristics information. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure apparatus that includes an exposure head provided with a plurality of organic EL light emitting elements, and exposes a photosensitive material by emitting a light beam from the plurality of organic EL light emitting elements.

  2. Description of the Related Art Conventionally, there has been known an exposure apparatus that includes an exposure head in which a plurality of light emitting elements are arranged in a predetermined direction, and that exposes the photosensitive material from the exposure head while relatively moving the exposure head and the photosensitive material. It has been.

  In this type of exposure apparatus, if there is a variation (deviation) in the intensity of the light beam emitted from each light emitting element, the same drive conditions (drive voltage, drive current, light emission) are used to record pixels of the same density. Even if each light emitting element is caused to emit light in a time period or the like, there is a case where a variation occurs in the amount of light to be irradiated and a streak unevenness occurs in a recorded image.

  For this reason, this type of exposure apparatus is provided with a light amount detection sensor, which causes each light emitting element to emit light under the same driving conditions, and moves the light amount detection sensor in a predetermined direction with respect to the exposure head, and each light emission by the light amount detection sensor. Measure the light quantity of the light beam emitted from the element, obtain a light quantity correction coefficient that equalizes the light quantity emitted from each light emitting element based on the measurement result, and use the above light quantity correction coefficient when actually exposing the photosensitive material. Some light emitting elements are driven under the corrected driving conditions to achieve uniform exposure (see, for example, Patent Document 1).

  By the way, in the exposure head, as an exposure light source for exposing the photosensitive material, a light emitting element such as an LED (light emitting diode) and a fluorescent display tube, and PLZT (lead, which modulates transmitted light emitted from the light source). Some of them employ light modulation elements such as lanthanum, zirconium, and titanium composite oxides) and liquid crystals, but recently, some employ organic EL (electroluminescence) light-emitting elements.

  However, since the organic EL light emitting element has a large luminance drop due to the accumulated light emission time compared to other light emitting elements and light modulation elements, when the exposure head is driven over a long period of time, the exposure amount decreases and the print density changes. End up. For this reason, when the organic EL light-emitting element is employed as the exposure light source, it is essential to periodically correct the variation in the light amount. As described in Patent Document 1 described above, the light amount detection sensor is mounted in the exposure apparatus and periodically. It is necessary to correct the light amount deviation.

  Conventionally, it has been known that an organic EL light emitting element has a phenomenon called edge growth in which a light emitting area of a light emitting region decreases with time even in a non-driven state. The problem is that the amount of emitted light is reduced due to the reduction of the light emitting area due to.

Therefore, as a technique for solving this problem, Patent Document 2 and Patent Document 3 disclose the configuration of an organic EL light-emitting element that can suppress the occurrence of edge growth. When used in a display device, it has reached a level where the occurrence of edge growth does not become a problem.
JP-A-10-185684 JP 2005-5227 A JP 2001-57286 A

  However, even when the techniques of Patent Document 2 and Patent Document 3 are used, the occurrence of edge growth over time of the organic EL light-emitting element is not completely eliminated, and the exposure of exposing the photosensitive material by the inventor's research. The effect of edge growth when an organic EL light emitting element is used for the head has been clarified.

  That is, when edge growth occurs and the light emission area decreases, it is easily conceived that the exposure amount for exposing the photosensitive material decreases. This decrease in the exposure amount is corrected by the light quantity deviation correction of Patent Document 1 described above. I think it can be done.

  However, the effect of the decrease in the light emitting area of the organic EL light emitting element is not only the decrease in the exposure amount, but when printing an image on a photosensitive material such as a silver halide photosensitive material, the gradation of the print is reduced as the light emitting area decreases. There is a problem that the characteristics are softened and a stable print quality cannot be obtained.

  FIG. 18 is a graph showing print gradation characteristics when the silver halide photosensitive material is exposed when the light emitting area ratio of the organic EL light emitting element is 100%, 90%, 80%, 70%, and 55%. . In addition, this light emission area ratio is the ratio of the light emission area which decreased with time to the initial light emission area when the initial light emission area of the organic EL light emitting element is 100%. In FIG. 18, the light amount deviation correction is performed under one predetermined driving condition, and the luminance decrease due to the accumulated light emission time of each organic EL light emitting element is corrected.

  As shown in the figure, it can be seen that the print gradation characteristics become softer as the emission area ratio decreases.

  That is, by using the techniques of Patent Document 2 and Patent Document 3 as the configuration of the organic EL light-emitting element, when the organic EL light-emitting element is employed in a display device, a reduction in light emitting area due to the occurrence of edge growth does not become a problem. However, when the organic EL light-emitting element is used in an exposure head that exposes a silver halide photosensitive material, the reduction of the light-emitting area affects the print quality and is stable even if light intensity deviation correction is performed. There is a problem that it is impossible to obtain the print quality.

  The exposure head employs light-emitting elements such as LEDs, fluorescent display tubes, and organic EL light-emitting elements, and light modulation elements such as PLZT and liquid crystal as exposure light sources. In each element other than the organic EL light-emitting elements, A decrease in the light emitting area over time has not been confirmed, and the occurrence of edge growth is a problem limited to organic EL light emitting elements.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an exposure apparatus capable of obtaining a stable print quality.

  In order to achieve the above object, an invention according to claim 1 is provided with an exposure head provided with a plurality of organic EL light emitting elements, and each organic EL light emitting element is driven at a constant current to emit a light beam. An exposure apparatus that exposes an image represented by image data on a material, the measuring means for measuring a driving voltage applied to the organic EL light emitting element to drive the organic EL light emitting element at a constant current; Light emission area information indicating the relationship between the drive voltage and the light emission area of the light emitting region of the organic EL light emitting element, and when the organic EL light emitting element emits light with each light emitting area for each of a plurality of predetermined light emitting areas Measured by the measuring unit based on the storage unit storing gradation characteristic information indicating the gradation characteristic of the photosensitive material in advance and the light emission area information stored in the storage unit. Deriving means for deriving the light emitting area from the driving voltage, and the gradation characteristic information corresponding to the light emitting area derived by the deriving means from the gradation characteristic information for each light emitting area stored in the storage means. Selection means for selecting, and gradation conversion means for performing gradation conversion on the image data using the gradation characteristic information selected by the selection means.

  According to the first aspect of the present invention, the driving voltage applied to the organic EL light emitting element to drive the organic EL light emitting element at a constant current is measured by the measuring means, and the driving voltage and the light emission of the organic EL light emitting element are measured. Light emission area information indicating the relationship with the light emission area of the region, and gradation characteristics indicating the gradation characteristics of the photosensitive material when the organic EL light emitting element emits light with each light emission area for each of a plurality of predetermined light emission areas Information is stored in advance in the storage means. The light emission area information may be an arithmetic expression indicating the relationship between the drive voltage and the light emission area, or may be a conversion table for converting the drive voltage and the light emission area. Further, the gradation characteristic information may be an arithmetic expression indicating the gradation characteristic of the photosensitive material for each light emitting area, or may be a gradation characteristic table. When the light emission area information and the gradation characteristic information are arithmetic expressions, the storage area required for storing each information can be reduced. When the light emission area information and the gradation characteristic information are used as a table, the light emission area derivation process and the gradation conversion process can be speeded up. The storage means includes a semiconductor memory such as a RAM and a flash memory, a portable memory such as a compact flash (registered trademark) and an xD picture card (registered trademark), and a fixed storage device such as a hard disk. The storage means for storing the light emitting area information and the gradation characteristic information may be physically different storage means.

  According to the invention, the light emitting area is derived from the driving voltage measured by the measuring means based on the light emitting area information stored in the storage means by the deriving means, and stored in the memory means by the selecting means. The gradation characteristic information corresponding to the light emission area derived by the deriving means is selected from the gradation characteristic information for each emission area, and the gradation characteristic information selected by the selection means is used by the gradation conversion means. Thus, gradation conversion is performed on the image data. Note that the light emitting area of the light emitting region is not necessarily an absolute value, and may be a change rate with time of the light emitting area (light emitting area ratio = light emitting area / initial light emitting area).

  As described above, according to the first aspect of the present invention, the light emission area information indicating the relationship between the drive voltage and the light emission area of the light emission region of the organic EL light emitting element, and a plurality of predetermined light emission areas, The gradation characteristic information indicating the gradation characteristic of the photosensitive material when the organic EL light emitting element emits light with the light emitting area is stored in advance in the storage means, and the organic EL light emitting element is driven to drive the organic EL light emitting element at a constant current. A driving voltage applied to the element is measured, a light emitting area is derived from the measured driving voltage based on the light emitting area information stored in the storage means, and the floor for each light emitting area stored in the storage means is calculated. Since gradation characteristic information corresponding to the light emission area derived from the gradation characteristic information is selected and gradation conversion is performed on the image data using the selected gradation characteristic information, stable print quality can be obtained. .

  According to the present invention, as in the invention described in claim 2, the storage means is configured to cause the organic EL light emitting element to emit light with a predetermined light emitting area instead of the gradation characteristic information for each light emitting area. Basic gradation characteristic information indicating gradation characteristics of the photosensitive material, and the basic gradation characteristic information corresponding to the light emitting area of the organic EL light emitting element for each of a plurality of predetermined light emitting areas. Conversion information for converting into information is further stored, and the selection unit converts the conversion information corresponding to the light emission area derived by the deriving unit from the conversion information for each light emission area stored in the storage unit. The basic gradation characteristic information stored in the storage means is converted into the gradation characteristic information corresponding to the light emitting area of the organic EL light emitting element based on the conversion information selected by the selection means. Further comprising a tone characteristic converting unit, the gradation conversion unit may performs gradation conversion with respect to the image data by using the tone characteristic information converted by the gradation characteristic conversion means.

  In the invention according to claim 1 or 2, as in the invention according to claim 3, the exposure head does not emit light at the time of exposure of the image, and the emission area of the organic EL light emitting element is derived. It is assumed that an organic EL light emitting element for deriving a light emitting area that emits light only is provided, and an organic EL light emitting element for measuring a driving voltage by the measuring means is an organic EL light emitting element for deriving the light emitting area. Also good.

  Further, according to the first or second aspect of the invention, as in the fourth aspect of the invention, the storage unit is configured such that the accumulated light emission time during which the organic EL light emitting element emits light and the amount of increase in the driving voltage are calculated. Voltage rise amount information indicating a relationship is further stored in advance, and a time measuring unit that measures the accumulated light emission time of the organic EL light emitting element, and the voltage increase amount according to the accumulated light emission time measured by the time measurement unit Correction means for correcting the drive voltage increase obtained from the information from the drive voltage measured by the measurement means, and the derivation means calculates the organic EL from the drive voltage corrected by the correction means. The light emitting area of the light emitting element may be derived. The voltage increase amount information may be an arithmetic expression indicating the relationship between the accumulated light emission time and the drive voltage increase amount, or may be a conversion table for converting the accumulated light emission time and the drive voltage increase amount. When the voltage increase information is an arithmetic expression, the storage area required for storing the voltage increase information can be reduced. When the voltage increase amount information is a table, the increase amount deriving process can be speeded up.

  As described above, according to the present invention, the light emitting area information indicating the relationship between the driving voltage and the light emitting area of the light emitting region of the organic EL light emitting element, and the organic EL in each light emitting area for each of a plurality of predetermined light emitting areas. The gradation characteristic information indicating the gradation characteristic of the photosensitive material when the light emitting element emits light is previously stored in the storage means, and is applied to the organic EL light emitting element in order to drive the organic EL light emitting element at a constant current. A drive voltage is measured, a light emission area is derived from the measured drive voltage based on the light emission area information stored in the storage means, and is derived from the gradation characteristic information for each light emission area stored in the storage means. The gradation characteristic information corresponding to the light emitting area selected is selected, and gradation conversion is performed on the image data using the selected gradation characteristic information, so that stable print quality can be obtained. Obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a schematic perspective view of an exposure apparatus 5 according to the first embodiment. In FIG. 1, the exposure head 1 is shown as an exploded perspective view.

  As shown in the figure, the exposure apparatus 5 moves the exposure head 1 and the color photosensitive material 3 held at the position where the light beam emitted from the exposure head 1 is irradiated in the sub-scanning direction (arrow Y direction). And a sub-scanning means 4 composed of two nip rollers and the like that are conveyed at a constant speed.

  The exposure apparatus 5 according to the present embodiment applies light beams of three colors, red (R), green (G), and blue (B), to the color photosensitive material 3 that is a full-color positive type silver salt photographic photosensitive material. It is supposed that a color image is recorded by irradiation.

  The exposure head 1 is disposed at a position for receiving an organic EL panel 6 and a light beam emitted from the organic EL panel 6, and forms a refractive index distribution type lens that forms an image of the light beam on the color photosensitive material 3 at an equal magnification. An array 7, a holding unit 8 that holds the lens array 7 and the organic EL panel 6, and a sealing member 60 that seals the organic EL panel 6 and protects it from moisture in the atmosphere. Yes.

  The organic EL panel 6 includes a line light emitting element array 6R that emits a red light beam, a line light emitting element array 6G that emits a green light beam, and a line light emitting element array 6B that emits a blue light beam. They are arranged side by side in the scanning direction Y. In the line-shaped light emitting element arrays 6R, 6G, and 6B, a large number of organic EL light emitting elements 20 (see FIG. 2) that emit corresponding R, G, and B light beams respectively extend along the main scanning direction (arrow X direction). Provided at predetermined intervals.

  The gradient index lens array 7 is a main scan in which a minute gradient index lens 7a that collects the light beams of the respective colors emitted from the respective linear light emitting element arrays 6R, 6G, 6B is orthogonal to the sub-scanning direction Y. A total of two lens rows arranged in parallel in the direction X are arranged, and a plurality of gradient index lenses 7a constituting one lens row are a plurality of lenses constituting the other lens row. It arrange | positions so that it may be located between the refractive index distribution type | mold lenses 7a.

  2 and 3 show the detailed structure of the exposure head 1 according to the first embodiment. 2 is a broken sectional view of the exposure head 1 in the main scanning direction X, and FIG. 3 is a broken sectional view of the exposure head 1 in the sub scanning direction Y.

  In the organic EL panel 6 according to the first embodiment, a plurality of transparent anodes 21 are formed along a sub-scanning direction Y on a transparent substrate 10 made of glass or the like, and on the transparent substrate 10 including the transparent anode 21 An organic compound layer 22 including a light emitting layer is formed, and three metal cathodes 23 are sequentially stacked on the organic compound layer 22 along the main scanning direction X. In the organic EL panel 6 according to the first embodiment, the middle metal cathode 23 among the three metal cathodes 23 arranged is formed longer than the other two (see FIG. 1). Further, 480 transparent anodes 21 are formed in the exposure area for the color photosensitive material 3, and one transparent anode 21 that intersects only the middle metal cathode 23 is formed outside the exposure area. Hereinafter, when only the transparent anode 21 outside the exposure area is distinguished from other transparent anodes, it is referred to as a transparent anode 21A.

  In the organic EL panel 6, when a voltage is applied to the metal cathode 23 and the transparent anode 21, a current flows through the organic compound layer 22 at the intersection of the electrodes to which the voltage is applied, and the light emitting layer contained therein emits light. The light beam is emitted through the transparent anode 21 and the transparent substrate 10. In the organic EL panel 6 according to the present embodiment, this light emitting intersection corresponds to one organic EL light emitting element 20. The organic EL light emitting element 20 can obtain a light beam of a desired color by appropriately selecting the material of the organic compound layer 22 including the light emitting layer.

  In the organic EL panel 6 according to the present embodiment, as shown in FIG. 4, 480 organic EL light emitting elements 20 for exposure are provided for each line-shaped light emitting element array 6R, 6G, 6B in the exposure area. In addition, one organic EL light emitting element 20A for measuring a light emitting area is provided outside the exposure area.

  As shown in FIG. 2, the surface of the organic EL panel 6 on which the organic EL light emitting element 20 is formed is covered with a sealing member 60 such as a stainless steel can so as to enclose the desiccant 61. It has been broken. The edge of the sealing member 60 and the transparent substrate 10 are bonded to each other, and the organic EL light emitting element 20 is sealed in the sealing member 60 replaced with dry nitrogen gas.

  By the way, in the exposure head 1, a light amount deviation occurs due to a variation in light emission characteristics of each organic EL light emitting element 20, an error in the mounting position of the lens array 7, and the like.

  For this reason, the exposure apparatus 5 according to the present embodiment further includes a photometric inspection apparatus 50 for measuring the amount of light of each organic EL light emitting element 20 of the exposure head 1.

  5 and 6 show a detailed configuration of the photometric inspection apparatus 50 according to the first embodiment. 5 is a front view of the photometric inspection apparatus 50 from the sub-scanning direction, and FIG. 6 is a plan view of the photometric inspection apparatus 50 from above.

  The photometric inspection device 50 includes a light receiving unit 51 that outputs an analog signal corresponding to the amount of received light, a moving unit 53 that holds the light receiving unit 51 and is loaded on a guide 52, and a light receiving surface of the light receiving unit 51. A light-shielding member 54 that covers the light-receiving surface in a state in which only the portion is viewed.

  In the exposure apparatus 5 according to the present embodiment, the guide 52 is provided along the main scanning direction including the range in which the light beam emitted from the exposure head 1 is irradiated.

  The photometric inspection device 50 is intermittently moved so as to face the exposure head 1 within the range irradiated with the light beam along the guide 52 when measuring the amount of light, and is conveyed when not measuring the amount of light. The guide 52 is retracted to the retracted position on one end side of the guide 52 that does not interfere with the material 3. In the present embodiment, the alignment pitch (hereinafter referred to as “element pitch”) in the main scanning direction X of the organic EL light emitting elements 20 provided in each of the line light emitting element arrays 6R, 6G, 6B is 100 μm. On the other hand, the intermittent movement pitch of the moving means 53 (hereinafter referred to as “photometric pitch”) is 5 μm. The light shielding member 54 has an elongated slit 54a extending in a direction perpendicular to the moving direction of the moving means 53 (sub-scanning direction Y), and the light receiving surface of the light receiving portion 51 is exposed only at the slit 54a. . The width of the slit 54a, that is, the photometric aperture length is 5 μm, which is the same as the photometric pitch.

  FIG. 7 shows the configuration of an electric system that controls the operation of the exposure apparatus 5 according to the first embodiment.

  The exposure apparatus 5 includes a drive circuit 30 that supplies driving power for causing each organic EL light emitting element 20 of the exposure head 1 to emit light, a light emission control unit 40 that outputs various signals such as light emission timing to the drive circuit 30, and an overall apparatus. And a system control unit 45 that performs control.

  The system control unit 45 includes a CPU 45A, ROM 45B, RAM 45C, a rewritable nonvolatile memory (not shown), and the like. The system control unit 45 outputs various correction data and the like to the light emission control unit 40 and outputs various instruction signals to the drive circuit 30. When the system control unit 45 receives image data from an external device (not shown), the system control unit 45 performs predetermined image processing such as resolution conversion on the received image data, and performs main scanning of an image indicated by the image data after image processing. Image data corresponding to each line in the direction is output to the light emission control unit 40 in order from the head side in the sub-scanning direction, and the light emission operation for each main scanning line is performed. The image data of one main scanning line includes density data of each color of R, G, and B for each pixel.

  The light emission control unit 40 includes a light emission timing control circuit 41, a gradation conversion unit 42, a light amount correction circuit 43, a light amount correction coefficient memory 44, and a gradation characteristic information storage unit 46.

  The gradation characteristic information storage unit 46 stores gradation characteristics of the color photosensitive material 3 when the organic EL light emitting element 20 emits light in each light emitting area for each of a plurality of predetermined light emitting areas of the organic EL light emitting element 20. Is stored in advance. In the present embodiment, the gradation characteristic information is defined as a print gradation conversion table in which an optimum target exposure amount corresponding to the density level is determined for each of R, G, and B colors. Are prepared for each light emitting area. Since the gradation characteristics depend on the material of the color photosensitive material 3 and the material of the light emitting element, it is preferable to prepare for each representative combination.

  The gradation characteristic information storage unit 46 outputs the print gradation conversion table designated by the table designation data input from the system control unit 45 to the gradation conversion unit 42. Prior to printing, the table designation data is output from the system control unit 45 according to the type of photosensitive material to be recorded.

  The gradation conversion unit 42 stores the print gradation conversion table input from the gradation characteristic information storage unit 46 as an LUT (Look Up Table) for gradation conversion, and is input from the system control unit 45 based on the LUT. From the R, G, and B densities of each pixel indicated by the image data to be obtained, a target exposure amount of each color of R, G, and B for exposing the pixel is obtained, and the image data is R, G of each pixel. , B is converted into exposure amount data indicating the target exposure amount for each color. The converted exposure amount data is output to the light amount correction circuit 43.

  The light amount correction circuit 43 performs a light amount deviation correction operation on the exposure amount data input from the light amount correction circuit 43 to obtain 8-bit light emission time data indicating the light emission time of each pixel for each of R, G, and B colors. . The obtained light emission time data for each color of R, G, and B is converted into serial data DATA and sequentially output to the drive circuit 30 for each color. In the present embodiment, the light emission time data is output to the drive circuit 30 in the order of R, G, and B.

  The light quantity correction coefficient memory 44 stores a light quantity correction coefficient for each organic EL light emitting element 20 of each color provided in each of the line light emitting element arrays 6R, 6G, and 6B. In the light quantity deviation correction calculation described above, an organic EL light emitting element that emits a light beam of a corresponding color used for exposure of the pixel with respect to the target exposure amount of R, G, B of each pixel indicated by the exposure amount data The light emission time for each color of R, G, B of each pixel is obtained by multiplying 20 light quantity correction coefficients. This light amount correction coefficient is preset from the system control unit 45 in the light amount correction coefficient memory 44 prior to printing.

  The light emission timing control circuit 41 outputs various signals under the control of the system control unit 45, outputs a serial load clock signal SR_CLK and a serial load signal SR_LOAD for controlling the operation to the drive circuit 30, and drives them. A light emission timing signal PWM_CLK indicating a light emission timing is output to the circuit 30 and a photometric timing control circuit 56 described later.

  The drive circuit 30 uses one of the three metal cathodes 23 as a scanning electrode corresponding to each color of R, G, and B, and the light emission time indicated by the light emission time data that is input to each transparent anode 21. The exposure head 1 is driven by a so-called passive matrix line-sequential selection driving method in which only the ON state is set.

  FIG. 8 is a block diagram illustrating an example of a detailed configuration of the drive circuit 30 according to the first embodiment.

  The drive circuit 30 includes a shift register 33, an 8-bit PWM circuit 34, an anode driver 32, a cathode driver 31, a line counter / decoder unit 37, a timing generation circuit 36, and a current / voltage setting unit 35. . The drive circuit 30 includes 3 channels of cathode drivers 31 corresponding to the three metal cathodes 23, respectively, and corresponds to a total of 481 transparent anodes 21 of 480 in the exposure area and one outside the exposure area. The anode driver 32 is provided with 481ch, but only one of them is shown in FIG.

  Serial data DATA indicating the light emission time of each organic EL light emitting element 20 is sequentially input to the shift register 33 in synchronization with the serial load clock signal SL_CLK. The input light emission time data is temporarily stored in the shift register 33. In the present embodiment, the shift register 33 accumulates light emission time data for 480 elements corresponding to the number of light emitting elements 480 in the exposure area of each of the line-shaped light emitting element arrays 6R, 6G, 6B. The accumulated light emission time data for 480 elements is output to the 8-bit PWM circuit 34 as the light emission time signal PWM_DATA for each light emitting element when the serial load signal SR_LOAD is input to the shift register 33.

  The 8-bit PWM circuit 34 converts the light emission time data for 480 elements indicated by the light emission time signal PWM_DATA input from the 8-bit PWM circuit 34 into a light emission pulse voltage signal PWMout of 256 steps. The converted light emission pulse voltage signal PWMout for 480 elements is output to the anode driver 32 in synchronization with the input of the light emission timing signal PWM_CLK.

  The anode driver 32 includes a switching unit 32A that individually connects each transparent anode 21 to a constant current source. When the light emission pulse voltage signal PWMout is input to the anode driver 32, each switching unit 32A is turned on for a time corresponding to the light emission pulse voltage signal.

  On the other hand, the timing generation circuit 36 is connected to the current / voltage setting unit 35 and the line counter / decoder unit 37 and receives the above-described light emission timing signal PWM_CLK. The timing generation circuit 36 outputs a timing signal to the current / voltage setting unit 35 every time the light emission timing signal PWM_CLK is input.

  The line counter / decoder unit 37 is connected to the cathode driver 31, and when a timing signal is input from the line counter / decoder unit 37, outputs an instruction signal instructing switching of the cathode driver 31.

  The cathode driver 31 includes a switching unit 31A that grounds each of the three metal cathodes 23 to bring it to the ground level. Each switching unit 31 </ b> A is individually turned on based on an instruction signal input from the line counter / decoder unit 37.

  The current / voltage setting unit 35 is connected to the anode driver 32 and the cathode driver 31, and the drive current and the drive voltage to the anode driver 32 are controlled by the current / voltage setting unit 35. The current voltage setting unit 35 individually controls the drive voltage so as to supply each anode driver 32 with a certain amount of current and drive each organic EL light emitting element 20 at a constant current.

  In the drive circuit 30 according to the present embodiment, the anode driver 32 is switched to the switching unit within each period in which the switching unit 31A is turned on and connected to the metal cathode 23 corresponding to each color of R, G, and B. By turning on each of 32 A, a certain amount of current flows through the organic compound layer 22 between the transparent anode 21 and the metal cathode 23, and light is emitted from the organic compound layer 22.

  The anode driver 32 and the cathode driver 31 are connected to the system controller 45. The system control unit 45 can control the anode driver 32 and the cathode driver 31 according to the instruction signal to individually control the on / off of the switching unit 32A and the switching unit 31A, and can emit specific light emitting elements.

  Further, the wiring connecting the anode driver 32 and the transparent anode 21A is branched and connected to the voltage measuring unit 38. The voltage measuring unit 38 is connected to a wiring whose other end is grounded, and measures the driving voltage applied to the organic EL light emitting element 20A by measuring the potential of the transparent anode 21A. The measured drive voltage of the organic EL light emitting element 20A is output to the system control unit 45 as drive voltage data.

  When the system control unit 45 causes the organic EL light emitting element 20A outside the exposure area to emit light and the drive voltage data is input from the voltage measurement unit 38, the system control unit 45 performs a print gradation conversion table designation process described later, based on the drive voltage data. The light emission area of the organic EL light emitting element 20A is obtained, and table designation data for designating a print gradation conversion table corresponding to the light emission area is output to the gradation characteristic information storage unit 46.

  On the other hand, as shown in FIG. 7, the exposure apparatus 5 further includes an inspection apparatus control unit 55 that controls the operation of the photometric inspection apparatus 50 described above.

  The inspection apparatus control unit 55 includes a photometric timing control circuit 56 that controls the photometric timing of the photometric inspection apparatus 50, an amplifier 57 that amplifies the analog signal output from the photometric inspection apparatus 50, and an AD that converts the analog signal into digital data. Converter 58.

  In the inspection device control unit 55, an analog signal indicating the amount of light output from the light receiving unit 51 of the photometric inspection device 50 is amplified by the amplifier 57, converted into digital photometric data by the AD converter 58, and output to the system control unit 45. The

  The system control unit 45 calculates a light amount correction coefficient for each organic EL light emitting element 20 of each color provided in each of the line-shaped light emitting element arrays 6R, 6G, and 6B based on the photometric data input from the inspection apparatus control unit 55. To do. The calculated light amount correction coefficient is stored in the light amount correction coefficient memory 44 in association with each organic EL light emitting element 20.

  Next, the overall operation when exposure is performed by the exposure apparatus 5 according to the first embodiment will be briefly described.

  When receiving the image data from the external device, the system control unit 45 sequentially outputs image data corresponding to each line in the main scanning direction of the image indicated by the image data to the light emission control unit 40. Further, the system control unit 45 controls the driving of the sub-scanning means 4 in synchronization with the output of the image data to start the conveyance of the color photosensitive material 3 in the sub-scanning direction Y.

  In the light emission control unit 40, when the image data is input from the system control unit 45, the gradation conversion unit 42 converts the density of R, G, B of each pixel indicated by the image data by the LUT and converts the R, G, and B of each pixel. The exposure amount data indicating the target exposure amount for each color of G and B is obtained, and the light amount correction circuit 43 performs a light amount deviation correction operation on the exposure amount data to obtain light emission time data for each color of R, G, and B. The light emission time data is output to the drive circuit 30 in the order of R, G, and B.

  The drive circuit 30 first accumulates the light emission time data for 480 elements of R input in the shift register 33, and the 8-bit PWM circuit 34 converts the light emission time data of R into a light emission pulse voltage signal PWMout of 256 steps.

  Then, when the light emission timing signal PWM_CLK is input, the drive circuit 30 turns on the switching unit 31A connected to the metal cathode 23 configuring the line light emitting element array 6R, and the switching unit 31A is turned on. In the period during which the anode driver 32 turns on each switching unit 32A for the time indicated by the first, second, third,... 480th emission time data of the main scanning line, the first, second, third,. Each transparent anode 21 of 480 is connected to a constant current source.

  Thereby, the current of the pulse width corresponding to the density of the pixel indicated by the image data on the organic compound layer 22 between the transparent anode 21 and the metal cathode 23 of each organic EL light emitting element 20 constituting the line light emitting element array 6R. Flows, and a red light beam is emitted from the organic compound layer 22.

  On the other hand, in the drive circuit 30, while the line-shaped light emitting element array 6R is emitting light, the light emission time data for 480 elements of G is accumulated in the shift register 33, and the light emission time data of G is 256 steps each in the 8-bit PWM circuit 34. Is converted into a light emission pulse voltage signal PWMout.

  Then, when the light emission timing signal PWM_CLK is input, the drive circuit 30 turns on the switching unit 31A connected to the metal cathode 23 that constitutes the line-shaped light emitting element array 6G, and as in the case of R described above, Within the period in which the switching unit 31A is in the on state, the anode driver 32 turns on each switching unit 32A for the time indicated by the first, second, third,... 480th emission time data of the main scanning line. The first, second, third,... 480 transparent anodes 21 are connected to a constant current source.

  Thereby, the pulse width corresponding to the density of the pixels to be recorded on the organic compound layer 22 between the transparent anode 21 and the metal cathode 23 of each organic EL light emitting element 20 in the light emitting area constituting the line light emitting element array 6G. Current flows, and a green light beam is emitted from the organic compound layer 22.

  On the other hand, the drive circuit 30 accumulates light emission time data for B 480 elements in the shift register 33 while the line-shaped light emitting element array 6G is emitting light, and the 8-bit PWM circuit 34 stores the light emission time data for B in 256 steps each. Is converted into a light emission pulse voltage signal PWMout.

  Then, when the light emission timing signal PWM_CLK is input, the drive circuit 30 turns on the switching unit 31A connected to the metal cathode 23 constituting the line-shaped light emitting element array 6B, and is the same as in the case of R and G described above. In addition, the anode driver 32 turns on each switching unit 32A for the time indicated by the first, second, third,..., 480th emission time data of the main scanning line within the period in which the switching unit 31A is on. The first, second, third,... 480 transparent anodes 21 are connected to a constant current source.

  As a result, a current having a pulse width corresponding to the density of the pixel recorded in the organic compound layer 22 between the transparent anode 21 and the metal cathode 23 of each organic EL light emitting element 20 constituting the line light emitting element array 6B flows. A blue light beam is emitted from the organic compound layer 22.

  The light beams of R, G, and B emitted from the organic EL panel 6 in this way are condensed on the color photosensitive material 3 by the lens array 7, and the first scanning line constituting the main scanning line is formed on the color photosensitive material 3. The first, second, third,..., 480th pixels are exposed to record a full-color main scanning line.

  Thereafter, the same processing is repeated for each main scanning line, and a two-dimensional color image composed of a large number of main scanning lines is recorded on the color photosensitive material 3.

  By the way, as described above, the organic EL light emitting element 20 has a decrease in luminance due to the accumulated light emission time, and when the exposure head 1 is driven for a long period of time, the light beam emitted from each organic EL light emitting element 20 Variations in intensity occur and streaks appear in the recorded image, or the exposure amount decreases and the print density changes.

  Therefore, in the exposure apparatus 5 according to the first embodiment, the light quantity correction coefficient for periodically measuring the light quantity of the light beam emitted from each organic EL light emitting element 20 by the photometric inspection apparatus 50 and correcting the deviation of the light quantity. Is derived.

  Next, the overall operation when the light amount correction coefficient is derived by the exposure apparatus 5 according to the first embodiment will be briefly described.

  The system control unit 45 controls the operation of the moving means 53 to position the photometric inspection device 50 at the retracted position on one end side of the guide 52.

  Then, the system control unit 45 causes each organic light emitting element 20 provided in each line light emitting element array 6R, 6G, 6B to emit light with the same light emission pulse width for each line light emitting element array. Image data having the same density is output to the light emission controller 40. At this time, the system control unit 45 sets all the light amount correction coefficients stored in the light amount correction coefficient memory 44 to 1. In the following description, an example in which each organic EL light emitting element 20 of the line light emitting element array 6R emits light and photometry is performed by the photometric inspection device 50 will be described.

  In the line-shaped light emitting element array 6R, all of the organic EL light emitting elements 20 are supplied with a constant current based on the same light emission time data, so that they are lit or isolated (all light emitting elements on one line) Are lit at the same time.

  The system control unit 45 intermittently moves the photometric inspection device 50 at a photometric pitch interval in the main scanning direction in synchronization with the organic EL light emitting element 20 that emits light, and is emitted from the lens array 7 by the light receiving unit 51 each time it stops. The amount of light beam is measured. The light receiving unit 51 outputs an analog signal corresponding to the amount of light beam. The analog signal is amplified by the amplifier 57, converted into digital photometric data by the AD converter 58, and output to the system control unit 45. Photometry is performed for each line-shaped light-emitting element array, and the light amount of each organic EL light-emitting element 20 is measured for the line-shaped light-emitting element arrays 6G and 6B in the same procedure.

  FIG. 9 shows an example of the beam profile of the light beam indicated by the photometric data.

  Based on the input photometric data, the system control unit 45 integrates for each organic EL light emitting element 20 over a section (100 μm) width equal to the element pitch of the organic EL light emitting element 20. Specifically, in the present embodiment, with respect to one organic EL light emitting element 20, the measurement light quantity relating to a total of 20 photometry points of 10 points in one direction of the main scanning direction and 10 points in the other direction from the center of the light emitting element. Add up and multiply by 1/20 to find an average value (moving average).

  In this case, it is not necessary to accurately determine the center position of the organic EL light emitting element 20, and it is confirmed that the 20 measurement points are distributed to the left and right from the center of the organic EL light emitting element 20. I can do it. Therefore, for example, it is considered that the element center exists between the measurement point A at which the maximum value of the light quantity is measured and the measurement point B having the larger measurement light quantity among the two adjacent measurement points of the measurement point. Move the measurement light quantity for 10 points (including measurement point A) from the measurement point A to the opposite side of the element center and 10 points (including measurement point B) from the measurement point B to the opposite side of the element center. What is necessary is just to use for calculation of an average value.

  The detection accuracy can be increased by integrating a plurality of light emission pulses rather than the integrated value of the first light emission pulse.

  Since this integrated light quantity is a value corresponding to the light quantity of the light beam, the system control unit 45 derives a light quantity correction coefficient that makes the integrated light quantity of each organic EL light emitting element 20 the same value, and derives each derived organic EL light emission. The correction coefficient for each element 20 is output to the light amount correction coefficient memory 44. The light amount correction coefficient is derived for each of the line-shaped light emitting element arrays 6R, 6G, and 6B.

  In the exposure apparatus 5 according to the present embodiment, as described above, the light amount deviation correction calculation is performed on the exposure amount data input from the light amount correction circuit 43 by the light amount correction circuit 43. The light intensity deviation characteristics of the light beams emitted from the organic EL light emitting elements 20 of the light emitting element arrays 6R, 6G, and 6B are corrected to be eliminated, and the occurrence of streak unevenness in the exposure image is prevented.

  By the way, in the organic EL light emitting element 20, as described above, edge growth occurs in which the light emitting area decreases even when the organic EL light emitting element 20 is not driven. This edge growth is a phenomenon in which the peripheral portion of the light emitting region is insulated or increased in resistance so that no current flows, and the peripheral portion becomes a non-light emitting region. When the organic EL light emitting element 20 is driven at a constant current, the current density of the current flowing through the remaining light emitting region increases as the edge growth progresses and the area of the light emitting region decreases, which is necessary for constant current driving. Drive voltage rises.

  On the other hand, as described above, the organic EL light emitting element 20 has a decrease in luminance as the accumulated light emission time becomes longer, and further, the drive voltage required for constant current driving increases as the accumulated light emission time becomes longer. It has occurred.

  Therefore, in the exposure apparatus 5 according to the first embodiment, only when the progress of edge growth is detected, the organic EL light emitting element 20A provided outside the exposure area is caused to emit light by constant current driving, and the organic EL The light emission area is derived from the fluctuation amount of the drive voltage applied to the light emitting element 20A. Since the organic EL light emitting element 20A does not emit light when the color photosensitive material 3 is exposed, the accumulated light emission time is short, and the increase due to the accumulated light emission time included in the drive voltage is at a level that can be ignored.

  Next, an operation when selecting a print gradation conversion table having gradation characteristics according to the progress of edge growth in the exposure apparatus 5 according to the first embodiment will be described.

  The system control unit 45 outputs to the cathode driver 31 an instruction signal for turning on the switching unit 31A connected to the metal cathode 23 constituting the line-shaped light emitting element array 6G, and the switching unit connected to the transparent anode 21A. An instruction signal for turning on 32A is output to the anode driver 32.

  The cathode driver 31 turns on the switching unit 31A connected to the metal cathode 23 constituting the line-shaped light emitting element array 6G, and the anode driver 32 turns on the switching unit 32A connected to the transparent anode 21A. 21A is connected to a constant current source.

  Thereby, a green light beam is emitted from the organic EL light emitting element 20A.

  The voltage measurement unit 38 measures the drive voltage applied to the organic EL light emitting element 20A by measuring the potential of the transparent anode 21A at this time, and outputs the drive voltage data to the system control unit 45.

  When the drive voltage data is input, the system control unit 45 executes the following print gradation conversion table designation process.

  FIG. 10 shows a flow of print gradation conversion table designation processing according to the first embodiment. FIG. 10 is a flowchart showing the flow of processing of a print gradation conversion table designation processing program executed by the CPU 45B of the system control unit 45, and the program is stored in advance in a predetermined area of the ROM 45A.

  In step 102 in the figure, the current density of the light emitting region is derived from the drive voltage indicated by the drive voltage data.

  FIG. 11 shows an example of the relationship between the driving voltage and the current density when the organic EL light emitting element is driven at a constant current.

  As shown in the figure, when the light emission area decreases due to the occurrence of edge growth and the current density increases, the drive voltage also increases. Therefore, the current density can be predicted from the drive voltage applied to the organic EL light emitting element 20A. It can be said.

  Therefore, information indicating the relationship between the drive voltage and the current density as shown in FIG. 11 is stored in advance in the ROM 45B of the system control unit 45 as a drive voltage-current density conversion table.

  In step 102, the current density of the light emitting region is derived from the potential of the transparent anode 21A based on the drive voltage-current density conversion table stored in the ROM 45B.

  In the next step 104, the light emission area is derived from the current density derived in step 102.

  FIG. 12 shows an example of the relationship between the current density of the remaining light emitting region and the light emitting area. In FIG. 12, the light emission area is shown as the light emission area ratio indicating the ratio of the light emission area after aging when the initial light emission area is 100%.

  As shown in the figure, the current density and the light emission area ratio are in a proportional relationship, and as the current density increases, the light emission area ratio decreases and the light emission area decreases. Therefore, the light emission area can be obtained from the current density.

  Therefore, in the present embodiment, information indicating the relationship between the current density and the light emission area is stored in advance in the ROM 45B of the system control unit 45 as a current density-light emission area conversion table.

  In step 104, the light emission area is derived from the current density based on the current density-light emission area conversion table stored in the ROM 45B.

  In the next step 106, among the print gradation conversion tables stored in the gradation characteristic information storage unit 46 based on the light emission area based on the derived light emission area, the print gradation conversion table corresponding to the light emission area. Is output to the gradation characteristic information storage unit 46, and the print gradation conversion table specifying process is terminated.

  The gradation characteristic information storage unit 46 outputs the print gradation conversion table designated by the table designation data to the gradation conversion unit 42. The gradation conversion unit 42 stores the print gradation conversion table input from the gradation characteristic information storage unit 46 as a gradation conversion LUT.

  As a result, the tone conversion unit 42 uses the R, G, and B densities of each pixel indicated by the image data based on the stored LUT to target the R, G, and B colors for exposing the pixel. Since gradation conversion for determining the amount is performed, a target exposure amount having gradation characteristics corresponding to the light emitting area of the organic EL light emitting element 20 can be obtained. Therefore, the exposure apparatus 5 can prevent the soft gradation of the print gradation characteristics of the recorded image generated due to the reduction of the light emission area due to the occurrence of edge growth, and can obtain a stable print quality.

  In the print gradation conversion table designating process according to the first embodiment, the current density is once derived based on the drive voltage-current density conversion table stored in the ROM 45B from the potential of the transparent anode 21A (step). 102) The light emission area ratio is derived from the derived current density based on the current density-light emission area conversion table stored in the ROM 45B (step 104). However, the present invention is not limited to this. Based on the relationship between the drive voltage and the current density shown in FIG. 11 and the relationship between the current density and the light emission area shown in FIG. 12, the system control unit 45 generates a drive voltage-light emission area conversion table for converting the drive voltage and the light emission area ratio. The ROM 45B may be stored in advance, and the light emission area may be derived from the drive voltage based on the drive voltage-light emission area ratio conversion table. There.

  As described above, according to the first embodiment, the exposure head including the plurality of organic EL light emitting elements is provided, and each organic EL light emitting element is driven at a constant current to emit a light beam, thereby generating a photosensitive material ( Here, it is an exposure apparatus that exposes an image indicated by image data to the color photosensitive material 3), in order to drive the organic EL light emitting element at a constant current by the measuring means (here, the voltage measuring unit 38). The driving voltage applied to the organic EL light emitting element is measured, and the light emitting area information indicating the relationship between the driving voltage and the light emitting area of the light emitting region of the organic EL light emitting element (here, the driving voltage-current density conversion table and the current density) -Light emission area conversion table) and gradation characteristic information (grayscale characteristic information indicating the gradation characteristics of the photosensitive material when the organic EL light emitting element emits light in each light emission area for each of a plurality of predetermined light emission areas. Here, the print gradation conversion table is stored in advance in the storage means (here, the ROM 45B and the gradation characteristic information storage unit 46), and the derivation means (here, step 102 of the print gradation conversion table designation process) In step 104), the light emission area is derived from the driving voltage measured by the measurement unit based on the light emission area information stored in the storage unit, and the selection unit (here, step 106 of the print gradation conversion table designation process). To select gradation characteristic information corresponding to the light emission area derived by the deriving means from the gradation characteristic information for each light emitting area stored in the storage means, and select gradation conversion information (in this case, the gradation conversion unit 42). ), Gradation conversion is performed on the image data using the gradation characteristic information selected by the selection means. It is possible to obtain.

  Further, according to the first embodiment, the exposure head emits light only when deriving the light emitting area of the organic EL light emitting element without emitting light when exposing the image (here, the organic EL light emitting element (here, The organic EL light emitting element 20A) is provided, and the organic EL light emitting element whose driving voltage is measured by the measuring means is the organic EL light emitting element for deriving the light emitting area. The light emission area can be derived from the fluctuation amount of the drive voltage without being affected by the increase.

  In the first embodiment, the gradation characteristic information storage unit 46 stores in advance a plurality of print gradation conversion tables indicating the gradation characteristics of the color photosensitive material 3 for each light emitting area of the organic EL light emitting element 20. However, the present invention is not limited to this. For example, the photosensitive material when the organic EL light emitting element 20 emits light with a predetermined light emitting area in the gradation characteristic information storage unit 46 is described. A print gradation conversion table indicating gradation characteristics is stored as basic gradation characteristic information, and the basic gradation characteristic information is printed for each of a plurality of predetermined light emission areas, corresponding to the light emission area of the organic EL light emitting element. Conversion information for conversion into a tone conversion table is further stored, and the system control unit 45 converts the light emission area derived by the print tone conversion table designation process. Designation data selected from the conversion information for each light emitting area stored in the gradation characteristic information storage unit 46 is output to the gradation characteristic information storage unit 46, and the conversion designated by the gradation characteristic information storage unit 46 Based on the information, the basic gradation characteristic information is converted into a print gradation conversion table corresponding to the light emitting area of the organic EL light emitting element 20, and the print gradation conversion table is output to the gradation conversion unit 42. The print gradation conversion table may be used to perform gradation conversion on the image data. Thereby, since it is not necessary to store a plurality of tables in the gradation characteristic information storage unit 46, the capacity of a necessary storage area can be reduced.

[Second Embodiment]
In the second embodiment, a case will be described in which the progress of edge growth is detected from the organic EL light emitting element 20 that emits light by image exposure without providing the organic EL light emitting element 20A for measuring the light emitting area.

  FIG. 13 shows a schematic perspective view of the exposure apparatus 5 according to the second embodiment. In FIG. 13, the exposure head 1 is shown as an exploded perspective view. Note that the same components in FIG. 1 as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  In the exposure apparatus 5 according to the second embodiment, the organic EL light emitting element 20A is not provided in the exposure head 1, and the rest are the exposure apparatus 5 (FIG. 1) and the exposure head 1 ( The configuration is the same as that shown in FIGS.

  FIG. 14 shows the configuration of an electrical system that controls the operation of the exposure apparatus 5 according to the second embodiment. Note that the same components in FIG. 7 as those in FIG. 7 are denoted by the same reference numerals as those in FIG.

  The system control unit 45 is connected to the light amount correction circuit 43, and the light amount correction circuit 43 outputs the light emission time data together with the drive circuit 30 to the system control unit 45.

  The system control unit 45 measures the accumulated light emission time during which the predetermined organic EL light emitting element 20 emits light. That is, in the system control unit 45 according to the present embodiment, the light emission time of the pixel corresponding to the predetermined organic EL light emitting element 20 from the light emission time of 480 elements for each color of R, G, B indicated by the light emission time data. And is stored in the nonvolatile memory as accumulated light emission time data.

  FIG. 15 is a block diagram illustrating an example of a detailed configuration of the drive circuit 30 according to the second embodiment. Note that the same components in FIG. 8 as those in FIG. 8 are denoted by the same reference numerals as those in FIG.

  The drive circuit 30 according to the second embodiment includes three channels of cathode drivers 31 corresponding to the three metal cathodes 23, and anode drivers 32 corresponding to the 480 transparent anodes 21 in the exposure area. It has 480ch.

  The wiring connecting the anode driver 32 and each transparent anode 21 is branched and connected to the input terminal of the multiplexer 39, and the output terminal of the multiplexer 39 is connected to the voltage measuring unit 38.

  The multiplexer 39 can selectively connect any one of a plurality of input terminals to the voltage measurement unit 38 under the control of the system control unit 45. The voltage measurement unit 38 measures the potential of the connected transparent anode 21 and outputs drive voltage data to the system control unit 45.

  That is, in the driving circuit 30 according to the second embodiment, the transparent anode 21 connected to the voltage measuring unit 38 is switched by the multiplexer 39 and the potential of each transparent anode 21 is measured, whereby each organic EL light emitting element 20 is measured. The drive voltage can be measured.

  Next, an operation when selecting a print gradation conversion table having gradation characteristics according to the progress of edge growth in the exposure apparatus 5 according to the second embodiment will be described.

  The system control unit 45 outputs an instruction signal to control the cathode driver 31 and the anode driver 32 to cause the predetermined organic EL light emitting element 20 to emit light. Further, an instruction signal for connecting the multiplexer 39 to the transparent anode 21 constituting the predetermined organic EL light emitting element 20 is output.

  The multiplexer 39 selectively connects the input end connected to the transparent anode 21 constituting the predetermined organic EL light emitting element 20 under the control of the system control unit 45 to the voltage measurement unit 38. The potential of the transparent anode 21 of the organic EL light emitting element 20 is measured and driving voltage data is output to the system control unit 45.

  When the drive voltage data is input, the system control unit 45 executes the following print gradation conversion table designation process.

  FIG. 16 shows a flow of print gradation conversion table designation processing according to the second embodiment. In addition, about the process same as FIG. 10 of the figure, the code | symbol same part as FIG. 10 is attached | subjected, and the description is abbreviate | omitted.

  In step 100 in the figure, correction is performed by removing the drive voltage increase due to the accumulated light emission time from the drive voltage indicated by the drive voltage data.

  FIG. 17 shows an example of the relationship between the accumulated light emission time during which the organic EL light emitting element emits light and the drive voltage rise.

  As shown in the figure, since the amount of increase in the drive voltage increases as the accumulated light emission time becomes longer, it can be said that the amount of increase in the drive voltage due to the accumulated light emission time can be predicted from the accumulated light emission time.

  Therefore, voltage increase amount information indicating the relationship between the accumulated light emission time and the drive voltage increase amount as shown in FIG. 17 is stored in advance in the ROM 45B of the system control unit 45 as an accumulated light emission time-drive voltage increase amount conversion table. .

  In this step 100, an increase amount of the drive voltage corresponding to the accumulated light emission time is obtained based on the accumulated light emission time-drive voltage increase amount conversion table stored in the ROM 45B, and correction for removing the increase amount from the drive voltage is performed. Do.

  In the next step 102, the current density of the light emitting region is derived from the drive voltage corrected in step 100.

  Thereby, the progress of edge growth can be detected from the corrected drive voltage.

  In the present embodiment, the progress of the edge growth of all the light emitting elements is obtained from the driving voltage of one organic EL light emitting element 20, but the accumulated light emission time is measured in all the organic EL light emitting elements 20. In order to improve accuracy, it is desirable to average the light emission areas derived by measuring the drive voltages of all the organic EL light emitting elements 20 to obtain the average light emission area of the entire light emitting element array. However, if the number of elements to be measured increases, the processing time becomes longer due to the increase in the number of measurements and the number of calculations. Therefore, it is desirable to determine the number of elements to be measured according to the use of the exposure apparatus.

  As described above, according to the second embodiment, the storage unit stores voltage increase amount information (here, the drive voltage −) indicating the relationship between the accumulated light emission time of the organic EL light emitting element and the increase amount of the drive voltage. Current density conversion table) is further stored in advance, and a time measuring means (here, system control unit 45) for measuring the accumulated light emission time of the organic EL light emitting element, and a voltage according to the accumulated light emission time measured by the time measuring means. Correction means (in this case, step 100 of the print gradation conversion table designation process) for correcting the drive voltage increase obtained from the increase information from the drive voltage measured by the measurement means, and the derivation means Since the light emitting area of the organic EL light emitting element is derived from the driving voltage corrected by the correcting means, the driving voltage applied to the organic EL light emitting element that emits light upon exposure to the photosensitive material is derived. Because it can derive the area of the light emitting region by extracting the voltage rise due to the generation of Jjigurosu, there is no need to separately provide an organic EL light emitting element for emitting area measured exposure head.

  In the print gradation conversion table designating process of the first and second embodiments, the light emission area is derived. However, the light emission area is not an absolute value, for example, the initial light emission area is 100%. Alternatively, a light emitting area ratio represented by a ratio of a light emitting area after change with respect to the initial light emitting area may be used.

  Further, the present invention aims to correct the gradation characteristic variation due to the edge growth of the organic EL light emitting device 20, but as with the organic EL light emitting device 20, the light emitting area varies with time. Can achieve the same effect.

  In addition, the configuration of the exposure apparatus 5 described in the first and second embodiments (see FIGS. 1 to 8 and FIGS. 13 to 15) is merely an example, and is appropriately selected within the scope not departing from the gist of the present invention. Needless to say, it can be changed.

  The print gradation conversion table designation processing (FIGS. 10 and 16) described in the first and second embodiments is also an example, and can be appropriately changed without departing from the gist of the present invention. Needless to say.

  Further, the beam profile shown in FIG. 9 is also an example, and the relationship diagrams shown in FIGS. 11, 12, 17, and 18 are also examples, and are set as appropriate according to the actual configuration of the exposure head 1.

It is a perspective view which shows schematic structure of the exposure apparatus which concerns on 1st Embodiment. It is a fracture | rupture front view from the main scanning direction of the exposure head which concerns on 1st Embodiment. It is a fracture | rupture side view from the subscanning direction of the exposure head which concerns on 1st Embodiment. 1 is a plan view showing a detailed configuration of an exposure head according to a first embodiment. It is a front view from the sub-scanning direction of the photometric inspection apparatus according to the first embodiment. It is a top view from the upper part of the photometric inspection apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structure of the electric system of the exposure apparatus which concerns on 1st Embodiment. 1 is a block diagram illustrating a detailed configuration of a drive circuit according to a first embodiment. It is a figure which shows an example of the beam profile at the time of making one organic EL light emitting element of an exposure head light-emit. 6 is a flowchart illustrating a flow of print gradation conversion table designation processing according to the first embodiment. It is a graph which shows an example of the relationship between a drive voltage and current density. It is a graph which shows an example of the relationship between a current density and a light emission area. It is a perspective view which shows schematic structure of the exposure apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the electric system of the exposure apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the detailed structure of the drive circuit which concerns on 2nd Embodiment. It is a flowchart which shows the flow of the print gradation conversion table designation | designated process which concerns on 2nd Embodiment. It is a graph which shows an example of the relationship between accumulation light emission time and the raise amount of a drive voltage. It is a graph which shows the gradation characteristic change by the light emission area ratio change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure head 3 Color photosensitive material 5 Exposure apparatus 20 Organic EL light emitting element 38 Voltage measurement part 42 Tone conversion part 45 System control part 45B ROM
46 Gradation characteristic information storage unit

Claims (4)

An exposure apparatus that includes an exposure head provided with a plurality of organic EL light emitting elements and exposes an image indicated by image data on a photosensitive material by driving each organic EL light emitting element at a constant current to emit a light beam. There,
Measuring means for measuring a driving voltage applied to the organic EL light emitting element in order to drive the organic EL light emitting element at a constant current;
When the organic EL light emitting element emits light with each light emitting area for each of a plurality of predetermined light emitting areas and light emitting area information indicating the relationship between the driving voltage and the light emitting area of the light emitting region of the organic EL light emitting element Storage means for storing gradation characteristic information indicating the gradation characteristics of the photosensitive material in advance;
Derivation means for deriving the light emission area from the drive voltage measured by the measurement means based on the light emission area information stored by the storage means;
Selecting means for selecting the gradation characteristic information corresponding to the light emission area derived by the derivation means from the gradation characteristic information for each light emission area stored in the storage means;
Gradation conversion means for performing gradation conversion on the image data using the gradation characteristic information selected by the selection means;
An exposure apparatus comprising: Basic gradation characteristic information indicating gradation characteristics of the photosensitive material when the organic EL light emitting element emits light with a predetermined light emission area, instead of the storage means, instead of the gradation characteristic information for each light emission area; and Conversion information for converting the basic gradation characteristic information into the gradation characteristic information corresponding to the light emission area of the organic EL light emitting element for each of a plurality of predetermined light emission areas;
The selection means selects conversion information corresponding to the light emission area derived by the derivation means from the conversion information for each light emission area stored in the storage means,
Gradation characteristic conversion for converting the basic gradation characteristic information stored in the storage means into the gradation characteristic information corresponding to the light emitting area of the organic EL light-emitting element based on the conversion information selected by the selection means. Further comprising means,
The exposure apparatus according to claim 1, wherein the gradation conversion unit performs gradation conversion on the image data using the gradation characteristic information converted by the gradation characteristic conversion unit. It is assumed that the exposure head is provided with an organic EL light emitting element for deriving a light emitting area that emits light only when the light emitting area of the organic EL light emitting element is derived without emitting light during exposure of the image,
The exposure apparatus according to claim 1, wherein the organic EL light-emitting element whose drive voltage is measured by the measuring unit is the organic EL light-emitting element for deriving the light emission area. The storage means further stores in advance voltage increase amount information indicating a relationship between a cumulative light emission time during which the organic EL light emitting element emits light and an increase amount of the drive voltage,
Time measuring means for measuring the accumulated light emission time of the organic EL light emitting element;
Correction means for performing correction to remove the drive voltage increase obtained from the voltage increase information according to the accumulated light emission time measured by the time measuring means from the drive voltage measured by the measurement means;
The exposure apparatus according to claim 1, wherein the deriving unit derives a light emitting area of the organic EL light emitting element from the drive voltage corrected by the correcting unit.